Centrifuge rotor



Jun'e 29, 1965 E. G. PIC'KELS ETAL 3,191,856

GENTRIFUGE ROTOR 3 Sheets-Sheet 1 Filed March 2'7, 1962 l I J FIG.

EDWARD G. PICKELS AND RICHARD C. STALLMAN ATTORNEYS FIG. 4

June 29, 1965 E. a. PICKELS ETAL 3,191,356

I CENTRIFUGE ROTOR Filed March 27. 1962 3 Sheets-Sheet 2 46 EDWARD G.PICKELS AND RICHARD c. STALLMAN 42x INVENTORS June 29,- 1965 s. a;PICKELS ETAL 3,

cmmuea ROTOR Filed March 27, 1962 s Sheets-Sheet a EDWARD G. PICKELSAND. RICHARD C. STALLMAN INVENTORS ATIQRNEYS' United States Patent3,191,856 CENTRIFUGE ROTOR Edward G. Pickels, Atherton, and Richard C.Stallman, San Carlos, Calih, assignors to Bechman Instruments, Inc., acorporation of California FiledMar. 27, 1962, Ser. No. 182,912 2 Claims.(Cl. 233-6) This application is a continuation-in-part of our earlierfiled copending application Serial No. 732,617, filed May 2, 1958, nowabandoned.

The present invention relates generally to a centrifuge and moreparticularly to a centrifuge rotor.

Continuous flow centrifuge rotors of the prior art have some drawbackswhen employed for laboratory use. For example, they have a relativelylarge hold-up volume and there are no satisfactory means forreconstituting'the sediment which is collected on the walls of therotor.

It is a general object of the present invention to provide an improvedcentrifuge rotor.

It is another object of the present invention to provide a continuousflow centrifuge having a relatively small hold-up volume.

It is another object of the invention to provide a centrifuge rotorhaving an inverted rotatable bowl-like member for reducing the hold-upvolume and also providing means for reconstituting sediment.

These and other objects of the invention will become more clearlyapparent from the following description when taken in conjunction withthe accompanying drawings.

Referring to the drawing:

FIGURE 1 is a side elevational view, partly in section, showing acomplete centrifuge apparatus;

FIGURE 2 is an enlarged sectional view showing a continuous flowcentrifuge rotor assembly and system;

FIGURE 3 is a sectional view along the line 3-3 of FIGURE 2;

FIGURE 4 is atop view of the inner bowl of a rotor assembly inaccordance with the invention;

FIGURE 5 is a top view of the central bowl of a rotor assembly inaccordance with the invention; and

FIGURE 6 is a bottom view of the central bowl of a rotor assembly inaccordance with the invention.

Referring to FIGURE 1, a centrifuge apparatus having an outer housing 11which encloses the working parts is illustrated. The top of the housingis provided with an opening 12.through which the rotor 13 may beinstalled and removed. A sliding door 14 having a louvered opening 16provides access to the rotor 13. The door is provided with spacedrollers17 which ride in the channels 18 secured to the sides of the housing 11.A latch mechanism (not shown) works in conjunction with the controls(not shown) to release the door whereby it may be opened. The louveredopening allows circulation of air through the rotor chamber, as will bepresently dcscribed.

The rotor is disposed within a cylindrical chamber 19 which acts as aguard in the event of breakage or explosion of the rotor under thestrains occasioned at the relatively high operating speeds at which itis operated. The louvers 20 are so slanted that if breakage shouldoccur, none of the pieces will fly out.

The cylindrical chamber 19 is mounted on a base 21 by a plurality ofpins 22 which are suitably secured to the bottom of the cylinder .and tothe base. The pins 22 serve to hold the bottom edge of the cylinder 19spaced from the base 21 whereby air may circulate through the spacebetween the cylinder 19 and the base 21. Thus, the air may circulatedownward through the louvered opening in the door, past the rotor, andoutwardly through 3,191,856 Patented June 29, 1965 ice lower space.Circulation is caused by the air currents set up by the rapidly rotatingrotor 13. l

The rotor 13, to be presently described in detail, is mounted on the endof a flexible drive shaft 23. The bottom end of the shaft is journalledin the hearing assembly 24 which is filled with oil to continuouslylubricate and cool the bearing as the rotor is driven. A replaceablegear 26 is adapted to drive the shaft 23. A drive belt 27 engages thegear 26 and a gear 28 driven by a motor 29 mounted on the base 21 bymeans of a bracket 30.

A removable plate 31 is carried at the bottom of the rotor chamber topermit changing the gear 26 for speed changes. Apparatus in accordancewith the foregoing is described in detail in Patent No. 2,878,992.

A member 33 is threadably received by sleeve Zila carried by the louvers20 formed in the cover 14. The member serves to slidably receive theassembly 34, to be presently described in detail, which feeds andremoves sample material from the rotor.

Referring to FIGURE 2, a sectional view of a suitable rotor assembly andassembly 34 is shown. The rotor assembly shown comprises an inner bowl41 which is threadably received by the lower end 42 of an outer bowl 43to nest within the same in spaced relationship therewith. An O-ring 44-provides a suitable seal between the two bowls. The inner bowl includesa coaxial collar 46 which receives the upper end of the shaft 23. Thepins 47 seat in accommodating recesses (not shown) formed in the shaft23, whereby the rotor assembly is driven by the shaft.

The upper surface of the inner bowl 41 includes a boss '48 having acentral recess 49. The boss is provided with a plurality of radiallyextending spaced slots 51 which terminate on a circular slot 52 (FIGURES2 and 4).

The outer bowl is provided with a threaded opening 54 which is adaptedto receive a nut 56. The lower end of the nut is suitably sealed to themember 43 by means of an O-ring seal 57. The bowls 41 and 43 cooperateto form a separating chamber. The central recess 49 of the inner bowland the interior of the not cooperate to form a sample supply andremoval chamber 60 which, as will, be presently described, receives themeans for supplying and removing fluid from the rotor assembly. Withinthis chamber there is disposed a central bowl or core 61. The sides ofthe bowl 61 extend downwardly into the chamber and adjacent to the lowerwall 62 of the same to thereby form two smaller separating chamberswhich are connected at their bottoms. The inner surface of the bowl isprovided with a lip 63 for purposes to be presently described. The lipextends inwardly to the outer surface of the inner bowl. However, thelip is not circular, as shown in FIGURE 6, whereby liquid can fiow pastthe 'lip. Preferably, the bowl or core is of such size that it occupiesa large percentage of the volume of the chamber to form a relativelysmall chamber 64 between its outer surface and the outer bowl, and arelatively small chamber 66 between its inner surface and the adjacentouter surface of the inner bowl 41. A disk-like insert 67 is provided atthe upper end of the bowl. It has an opening 68 which has a smallerdiameter than the recess 49 previously described. Thus, the insert 67acts as a dam subdividing the chamber 64) into two chambers so that oneserves to receive the fluid feed means and the other accommodates a pumpmeans. The member 67 is made of material which is self-lubricatingwhereby the central bowl rotates freely on the inner bowl. The uppersurface of the central bowl is provided with slots 69 which extendradially outwardly as shown in FIGURE 5. V

In operation, the liquid sample is fed into one portion of the samplechamber 69, passes down one of the charm 3 bers 64 or 66 around thelower edge of the bowl 61, and up the other passage 66 or 64, into theother portion of the chamber 60 where it is removed by the pumpingmeans.

Suitable means are provided for feeding the sample into one fluidchamber and removing the same from the other fluid chamber. Asillustrated in FIGURE 2, the sample is fed through the tube 71 of theassembly 34 into the fluid chamber including recess 49 where it travelsoutwardly along the slots 51 and downwardly in the separating chamber66. Sample material is removed through the annular passage 72 formedbetween the concentric tubes 71 and 73. The upper end of the annularpassage is connected to an outlet tube 76, and the lower end isconnected to a pump means designated generally by the reference numeral77 disposed in the fluid removal chamber.

The pump means includes an upper portion 78 having a tapered passageadapted to receive the lower end of the tube 73. The pump includes adisk 79 and scoops 81 disposed below the same. The scoops 81 areprovided with openings 82 (FIGURE 3) which communicate with the annularpassage 72. The liquid is scooped up as it is rotated past the scoopsand pumped upwardly in the annular passage to the outlet 76. Inoperation, the rotor is being spun at relatively high speeds and thescoop is stationary. The impact of the liquid in the scoops createssuflicient static pressure to cause pumping. It is, of course, apparentthat the design of the scoops shown is merely illustrative.

Thus, in operation, liquid is continuously fed by the tube 71 into thefluid feed chamber including recess 49. The liquid then flows outwardlybetween the bowls 41 and 61 along the slots 51 into the chamber 66,downwardly past the lip 63, across the surface 62, and upwardly in thechamber 64, and thence between the central bowl 61 and the outer bowl 43where it is collected (removed) by the pumping means in the fluidremoval chamber. An eX- planation of the forces which cause the fluid toflow through the rotor will be presently given.

It is desirable for ease of assembly that the tube 73 be removable fromthe pump. As described and illustrated, the pump is removable whereby itmay be dropped in the rotor and the nut 56 secured. The concentric tubesare then fed downwardly until the tapered end of the tube 73 engages thetapered opening formed in the pump. The tubes and pump are then lifteduntil the pump is free of the upper surface of bowl 61. Adjusting means84 is adapted to receive and hold the outer tube 73 of the concentrictubes. The arrangement includes an outer sleeve 86 which is threadablyreceived by the cover 14. The sleeve 86 slidably receives the tubes. Anut 87 is threaded into the sleeve 86 and has a lower tapered edge 88which is adapted to engage the outer surface of an O-ring 89 and urgethe same inwardly to lock the outer tube 73. Thus, by a turning movementof the nut 87, the outer tube may be locked in position. To open thecover 14, the adjusting means 84 is loosened and the pump means aredisconnected from the tube 73. The concentric tubes are removed from theadjusting means 84 and the adjusting means unscrewed from the cover 14.The cover is then free to slide open for removal of the rotor.

In certain applications it is desirable to operate the rotor with thesample in an atmosphere of inert gas. For this purpose, an opening 91formed in the sleeve 86 communicates with the space formed between atube 92 and the outer tube 73. The tube 92 is held within the sleeve bymeans of an O-ring 93. A member 94 is carried by the lower end of thetube and is held thereon by the shoulder 95 which engages the flaredlower portion 96 of the tube 92. Spring means 97 may be provided forurging the member 94 downwardly. The spring acts between the shoulder 98formed in the member and the shoulder formed by the ring 99 which issuitably secured to the cylinder at a spaced interval along the same.The member 94 is preferably made of a low friction material and has itslower edge in engagement with the machined sur: face 101 formed in theupper surface of the nut 56. Thus, inert gas may be continuously feddownwardly into the rotor.

Operation of the apparatus as described is then as follows: An O-ring ofa relatively hard material is placed on the surface of the central bowlwhereby the lower edge of the nut 56 locks the center bowl againstrotation with respect to the outer bowl. The liquid is fed, aspreviously described, whereby it flows in the inner chamber 66 and thelarger particles are collected by centrifugal force on the inner wall ofthe central bowl- 61. The solute flows downwardly past the lip but thecollected particles are trapped by the lip and held on the surface. Thesolute then flows upwardly in the chamber 64 where additional separationtakes place and is then pumped upwardly to the outlet 76.

If the liquid is to be reconstituted, the rotor may be removed from thechamber 19 and the nut 56 loosened whereby the central bowl is allowedto rotate freely. Suitable driving means may then be placed intoengagement with the central bowl at the notches 102 (FIGURE 5). Thechambers are filled with liquid and the central bowl is rotated. Therelative motion between the central bowl and the inner and outer bowlswill agitate the liquid and the collected particles are reconstituted.The reconstituted liquid in the rotor may then be drained.

It is observed that the apparatus is a continuous apparaus wherein thefluid is continuously fed and removed at the top of the rotor. Thehold-up volume, that is, the volume in the separating chamber, isrelatively small and, therefore, small amounts of liquid may beseparated. Further, means are provided for reconstituting the sediment.

We claim:

1. In a centrifuge, a rotor having inner and outer bowls securedtogether to form a cylindrical chamber therebetween, a central bowldisposed in said chamber, means formed to define a self-lubricatedbearing interface between said inner and central bowls, said interfaceextending transversely of the axis of rotation of the rotor and disposedto support said central bowl upon said inner bowl and to permti relativerotation therebetween, means rotatable with and secured to the outerbowl and formed to be axially movable between advanced and retractedpositions to respectively lock and unlock said outer bowl with respectto said central bowl, said central bowl being otherwise free to rotatein said chamber, the last named means including a nut threadedlyengaging said outer bowl and an O-ring disposed to be pinched betweensaid nut and said central bowl when said nut is in its advanced positionto frictionally lock said outer and central bowls to provide conjointrotation of all said bowls during a centrifugation and, when said nut ismoved to its retracted position, to permit rotation of said central bowlin said chamber.

2. In a centrifuge, a rotor having inner and outer bowls securedtogether to form a cylindrical chamber therebetween, a central bowldisposed in said chamber, means formed to define a self-lubricatedbearing interface between said inner and central bowls, said interfaceextending transversely of the axis of rotation of the rotor and disposedto support said central bowl upon said inner bowl and to permit relativerotation therebetween, and means rotatable with and secured to the outerbowl and formed to be axially movable between advanced and retractedpositions to respectively lock and unlock said outer bowl with respectto said central bowl, said central bowl being otherwise free to rotatein said chamber.

References Cited by the Examiner UNITED STATES PATENTS 560,635 5/96 Peck2336 585,936 7/97 Linders 23328 732,886 7/03 Odell et a1 233-14 (Otherreferences on following page) 5 UNITED STATES PATENTS Pihl 233-28 Nyrop233-7 Andersson 233-45 X Keet 233-27 X Lindgren 233-46 X Bergner 233-22Wilson 241-251 X Lindgren 233-22 X McBean 233-7 X Mayeaux 233-28 Pickelset a1. 233-22 X Trotter 23-3-7 6, FOREIGN PATENTS I 143,260 9/51Australia.

4,094 1894 Great Britain. 481,711 3/38 Great Britain.

5 877,128 1/54 Germany.

HARRY B. THORNTON, Primary Examiner.

ROBERT F. BURNETT, HERBERT L. MARTIN,

Examiners.

1. IN A CENTRIFUAGE, A ROTOR HAVING INNER AND OUTER BOWLS SECUREDTOGETHER TO FORM A CYLINDRICAL CHAMBER THEREBETWEEN, A CENTRAL BOWLDISPOSED IN SAID CHAMBER, MEANS FORMED TO DEFINE A SELF-LUBRICATEDBEARING INTERFACE BETWEEN SAID INNER AND CENTRAL BOWLS, SAID INTERFACEEXTENDING TRANSVERSELY OF THE AXIS OF ROTATION OF THE ROTOR AND DISPOSEDTO SUPPORT SAID CENTRAL BOWL UPON SAID INNER BOWL AND TO PERMIT RELATIVEROTATION THEREBETWEEN, MEANS ROTATABLE WITH AND SECURED TO THE OUTERBOWL AND FORMED TO BE AXIALLY MOVABLE BETWEEN ADVANCED AND RETRACTEDPOSITIONS TO RESPECTIVELY LOCK AND UNLOCK SAID OUTER BOWL WITH RESPECTTO SAID CENTRAL BOWL, SAID CENTRAL BOWL BEING OTHERWISE FREE TO ROTATEIN SAID CHAMBER, THE LAST NAMED